This invention pertains to a room-temperature fast-curing acrylate adhesive useful for structural applications including fiber optic connector assembly.
Presently, various methods are used to affix an optical fiber in a fiber optic connector so that the fiber does not move over time and during use. Movement of the fiber is problematic due to the potential for signal loss when two connectors are in alignment. One common method of securing the optical fiber in the connector is through use of an epoxy resin. Epoxy resins, however, are typically cured at high temperature when securing fibers in the connector. This adds cost to the installation process in that ovens are needed to effect curing at a reasonable rate. Typically, the curing occurs at 120° C. for about twenty minutes. The present inventors have recognized that a need exists for an adhesive which cures at room temperature to afford stable connections. The present inventors have determined that a solution to this problem would be highly desirable.
In an effort to find a solution to the problem, it was decided to investigate acrylate adhesives.
Acrylate adhesives are well known. For instance, U.S. Pat. No. 5,865,936, R. Edelman and W. J. Catena, describes the formulation of rapid curing two-part structural acrylate adhesives using a first part consisting of a mixture of acrylate and methacrylate monomers or oligomers, maleic acid, a hydroperoxide, and a source of ferric ions. A second part, the activator, is a substituted dihydropyridine.
U.S. Pat. No. 4,126,504, L. E. Wolinski and P. D. Berezuk, describes a fast-curing acrylate adhesive comprising of an elastomer dissolved in acrylate or methacrylate monomers initiated by benzoyl peroxide that is activated with a tertiary amine in the presence of an oxidizable heavy metal.
U.S. Pat. No. 4,112,013, P. C. Briggs, Jr. and L. C. Muschiatti, describes a room-temperature curing adhesive containing various acrylate monomers polymerized in the presence of a high amount (>20%) of either chlorosulfonated polyethylene or a mixture of chlorinated polyethylene and sulfonyl chloride. The method utilizes a peroxide as a free-radical generator, an organic salt of a transition metal as a promoter, an aldehyde-amine condensation product as an accelerator, and a tertiary amine as an initiator. These adhesives may be formed as a two-component system or as a primer system. A similar method for room-temperature cure adhesives is described in U.S. Pat. No. 4,263,419 by G. Piestert and H. G. Gilch.
However, the present inventors recognized that none of these references discloses an acrylate adhesive that cures at room temperature and is dimensionally stable under load. The present inventors recognized that a need existed for such an adhesive.